Expansion roof structure with counterbalancing means



April 17, 1945. A. WlLKlN 7 3 3- EXPANSION ROOF STRUCTURE WITH COUNTERBALANCING MEANS Filed Dec. 4, 1941 3 Sheets-Sheet 1 INVENTOR.

April 17, .1945.- w Kl v 2,373,797

I EXPANSION ROOF STRUCTURE WITH COUNTERBAL'ANCING MEANS Filed Dec.'4, 1941 3 Sheets-Sheet 2 1N VENT: OR.

BY Z6522? (2 WM,

April 11, 1945. L A, W'LKIN 2,313,791

EXPANSION ROOF STRUCTURE WiTH COUNTERBALANCING MEANS Filed 1:50. 4, 1941 s Sheets-Sheet roof tanks;

Patented Apr. 17, 1945 UNITED STATES v 7 2,372,797 I 1 EXPANSION ROOF STRUCTURE WIT-H.

COUNTERBALANCING; MEAN S} Lester. A. Wilkin,.East Chicago, Ind., assignor. to

Graver Tank.& .Mfg. Co

Inc, Catasauqua, Paz, I acorporation of Delaware Application December 4,1941,seriauvo.421,530

2 Claims.

The invention relates to expansion roof tanks and has moreparticular reference-toan expansion roof of the launder type whereinguide posts depending from the roof are connected by'flexible cables tc-provide 'stabilizing'means for controlling 1 vertical movements of the roof whereby thevapor space within the tank'may be varied.

The present inventionis an improvement over that shown in the Lester A. Wilkin and? Charles. L. Marner Patent No. 2,287,586 issued-June 23, 1942, for Outside'stabilizing means for expansion In that application it is explained that upward:verticalmovement, of'the-roof to increase the vapor space within. the tank is necessary toretain the volatile vapors. produced during theheat of'the day so that the vapors can be 'condensedby the cooler night temperature. 'These volatilefactions are therebyconserved" and substantially the same procedure takes place upon filling of expansion roof storagev tanks since the filling operationincreasesthp production. of. va pors. which are accommodated by the upward movement of the roof, thereby maintaining asubstantially uniform pressure on the roof.

Unless counter-balancing means are employed the vapor pressure necessary to. cause movement of the expansion roof in an upward directionis determined. primarily by the weight of the roof including the weight of stabilizing means having fixed relationthereto and which move. with the roof. However, by counter-balancing the dead weight of such a roof it is possible to secure operation. at much lower pressures. Operation at these low pressures is desirable since thevapor space in an expansion roof tankis often connectedwith the vapor space of ordinary roof tanks built to safely withstand a very low maximum vapor pressure.

An object of the invention is toprovide counter-balancing means for a movable. roof of the "gas holder type having outside stabilizing, mecha- In the: drawings: which. illustrate an; embodiment of" thedeviceand wherein like reference 'characters are used to designate. like parts- Figure-1 is anielevational viewof an expansion improved... counter balancing means associated therewith;

' Figiuref3: is :afragmentary horizontal sectional view showing the location .ofuthe dependingposts and. sheaves; circumferentially of: the tank;

Figure; 4. is. a fragmentary vertical sectional view." takensubst-antially along line 4-4 of Figure 2 showing. a. depending postand the mechanism connecting flexible cables; and

Figure 5 is a fragmentary vertical sectional view taken along line 5'-5 of Figure'Z and more particularly showing the'doubl'e sheave structure-re I quired for the counter balancing Weight.

In Figure 1" the invention is shown as applied to an expansion roof tank-having;cylindrical walls lflg a bottom H which may-rest directlyon'the' witlnn'th-e'structure- The cylindrical Wall's-Mat I their upper endsarev provided. with a launder l3 including a base or bottom member supported andsuitably reinforced at intervalsby the angle brackets l5, extending. inwardly from; the side walls Ill; The launder at its upper end is like- 0 wise reinforced by angle, members I6 which additionally provide supporting means whereby the rafters 11. are secured. to the. shell of. the tank. .The rafters have a slight inclination to provide a cone-shapedsupportingsurface for the .movable roof. l2 andsaid roof rests. upon therafters when in deflated position.

The movable, roof in. the. form of a holder bell includes a circular portion 18. for covering the entirearea; of the. opentop tank structure. Depending: fromvsaid. circular portion adjacent the periphery" thereof. is a skirt ZO-providing a dip ring with; respect tothe launder l3 andwhich I accordingly has location within said launder. The roof is completed by aperipheralportionv 2| weldedto the circumference'of the circular porassociated therewith including. sheaves and the 'tion l8 of the roof and which is substantially horizontal, as clearly shown in Figures 4 and 5. The inner end of the peripheral portion 2! has a depending strip 22 welded thereto which is backed up by the dip ring 20. The exterior edge is provided with a depending strip 23 and it will be understood that both said strips extend circumferentially around the roof. Strip 23 provides supporting means for the rain shed skirt 24 which is suitably welded to the exterior of the strip and depends vertically downward therefrom. The rain-shed skirt may be reinforced at intervals by angles 25 and the lower edge of said skirt is additionally strengthened by the angle 26 and the angle plates 21. The skirt 24 or weather hood is concentric with the depending dip ring 20, and the proper spaced relation is maintained with respect to the tank shell-to accommodate the stabilizing means for the roof.

Depending from the roof in spaced relation circumferentially of the roof are a plurality of posts 28 which are located midway between the rainshed skirt 24 and the cylindrical walls ill of the tank. Each post is secured to the roof at its upper end through a box-like structure including 1 depending side plates 29 and 30, Figure 2, which extend between strips 22 and 23, beingsuitably welded thereto, and which have approximately the same depth as the circumferential strips. Plates .29 and 34 support a bottom member 3| and a post 28 is suitably welded to said bottom plate. In this manner each "post has securement to the roof and the roof structure is reinforced above each post by the rib 32 which extends substantially radially of the roof.

Each post extends through openings in girders projecting outwardly from the tank shell. The top girder 33 extends completely around the tank and is strengthened by the vertical member 34 which is suitably welded to the outer edge of said girder. The girder 33 supports brackets 35 journalling rollers 36 having rolling contact with their particular depending post 28. A lower individual girder is associated with each depending post identified by numeral 31 and brackets 38 are supported in a like manner by these individual girders, each journalling rollers 39 also for guiding contact with their particular depending post. Girder 31 is suitably strengthened and reinforced by depending side plates 48 and 4| which are joined by a front end plate 42. This box-like structure, including the girder 31,.which can be considered as closing the top of the same, is welded to the shell of the tank and projects laterally from said shell in position to accommodate its particular depending post, as clearly shown in the drawings.

Flexible cables are provided for operatively connecting the depending posts with each other. More particularly the bottom of each post is connected by a chain with the top of an adjacent post in a direction toward the right, Figure 2. A plate 43 is weldedat the bottom of each post and the same retains an eye bolt 44 to which the flexible chain 45 is secured. Accordingly, a chain 45 has connection with the bottom of each post 7 and said chain extends upwardly, passing over a sheave 46 and then extends circumferentially of the tank shell until an adjacent post is reached, whereupon the chain passes under sheave 41 and then upwardly for connection with bottom plate 3| by means of the eye bolt 48. Sheave 46 is suitably journalled below girder 33 by the depending supports 50 which provide journalling means 5| Figure 4, for said sheave. The bottom of. each depending support 50 is joined by the base plate 52 suitably welded thereto and which is also welded to the tank shell. The sheave 41, Figure 5, is supported from girder 33 in a similar manner by depending supports 53 which likewise provide journalling means 54 for said sheave. The depending supports are secured to each other and to the tank shell by a base 55.

The structure for journalling sheave 41, which is positioned on the left hand side of each depending post, Figure 2, also journals a companion sheave 56 for the counter-balancing means to be presently described. Sheaves 46 and 41 are opposite each other since one is located on the right hand side of its respective depending post and the other on the left hand side of the post. Whereas, the flexible chain 45 passes over sheave 45 the said chain passes under sheave 41. Therefore during upward movement of the roof, sheave 46 will rotate clockwise and sheave 41 will rotate counter-clockwise. During downward movement of the roof the rotation of the respective sheaves is reversed.

It has been found desirable to counter-balance expansion roofs such as above described in order that the roof may operate on extremely low vapor pressures. In actual practice it is desirable that tanks equipped with expansion roofs operate on less than one ounce pressure per square inch. If such operation can be secured these expansion tanks can be used to store the vapors from a number of conventional fixed roof tanks. The resent invention proposes to counter-balance the movable roof I2 by the provision of a plural ity of counter-balancing weights 58, a weight being positioned in associated relation with each depending post. By means of the flexible chain 59 each counter-balancing weight is connected to the base of its respective depending post, the said chain passing over sheave 55 provided therefor and extending downwardly for connection to plate 43 which is efiected by means of the eye bolt 60. The counter-balancing weights 58 are therefore located on the exterior of the tank shell along with the stabilizing means including the depending posts 28 and the flexible chains 45 which operatively connect adjacent posts. Therefore the entire structure can be readily inspected and repaired and although the same is on the outside of the tank it is substantially protected from the weather by the rainshed skirt 24.

During operation of the movable roof the launder l3 will contain oil or water as a sealing medium for the dip ring 20 so that the interior of the tank is sealed from the atmosphere although the roof is free to move vertically to increase or decrease the vapor space within the tank. When-the vapor pressure within is sufficient to cause upward movement of the roof, the movement is controlled by the depending posts and the cables which connect the same. Each post is suitably guided during said movement and as a'result of the cables the entire roof is caused to move to the same extent and thus the roof during movement will maintain a substantially horizontal position. As previously explained, sheave 46 and sheave 41 for each depending post will rotate in opposite directions during upward and downward movement of the roof. However, sheave 41 and its companion sheave 56 for the counter-balancing means have rotation in unison and in the same direction. This takes place notwithstanding that the cable 45 passes under sheave 41, whereas, cable 59 roof in spaced relation circumierentially thereof and located externally of the tank, a girder passes over sheave 56. The action of each coun ter-balancing weight 58 is to urge the roof I 2 upwardly, this said force being communicated to the roof through the depending posts since the cable from the counter-balancing weight'has connection with the posts at the bottom end thereof." By proper adjustment of weights 58 the desired counter-balancing of themovable roof can be effected and the roof can be caused to move upwardly to increase the vapor space of the tank at very low maximum vapor pressures. v

Each flexible cable 45 connecting certain adjacent posts will include an intermediate portion between the sheaves 46 and 41 extending circumferentially of the tank. In Figure 2 this circumferential direction is towardthe right since each cable is fixed tothe bottom of the depending post on the left and has securement at its other end to the top of the depending post on the right. As the distance between posts in large tanks may be considerable, it has been found necessary to provide an intermediate pulley 6| projecting outwardly from the tank shell and located below the circumferential girder 33, The pulley contacts the intermediate portion of its respective cable 45 and by so doing positions the disposed laterally outward from the tank shell and having openings through which the posts extend, a single sheave supported by the girder on one side of each post, a pair'of sheaves supported.

by the girder .on the other side of each post, cables connecting certain posts to maintain the roof substantially horizontal during its up and down movements-each cable passing over its respective single sheave and passing under one of e a pair of sheaves, a flexible cable fixed to the endof each post and extending upward to pass over the other sheave of said pair and then depending downward therefrom, and a counter-balancingxweight fixed to the depending end of the central portion of the cable outwardly from the a tank shell so that no rubbing between the cable and tank shell will take place.

The invention is not to be limited to or by def tails of construction of the particular embodiment thereof illustrated by the drawings, asvarious other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is: I 1. In a tank having an expansion roof with sealing means between the roof and the tank shell, of a plurality of posts depending from the flexible cable.

2. In a tank having an expansion roof with sealing means between the roof and the tank shell, of aplurality of posts depending from the, roof in spaced relation circumferentially thereof and located externally of the tank, a girder dis- 7 posed laterally outward from the tank shell and having openings through which the posts extend, a single sheave supported from the undersurface of the girder on one side of each post, a pair of sheaves having 'a common axis and being supported from the undersurface of the girder on the other side of each post, cables connecting certain adjacent posts to maintain the roof substantially horizontal during its up and down 1 travel, each cable passing over its respective single sheave and passing under one of a pair of sheaves, another cable fixed to the end of each post and extending upward to pass over the other sheave of said pair and then depending downward therefrom, and a counter-balancing weight attached to the depending end of the last mentioned cable. p 7

' LESTER A; WILKIN. 

